earliest due date first.
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http://www. first served (FCFS): Jobs are processed in the order in which they arrive at a machine or work center. Shortest processing time (SPT): Jobs are processed according to processing time at a machine or work center. Compute by dividing slack time by number of remaining operations.edu.baskent. Rush: Emergency or preferred customers first.tr/~kilter
. Earliest due date (EDD): Jobs are processed according to due date. Slack per operation (S/O): Jobs are processed according to average slack time (time until due date minus remaining time to process). shortest job first. Critical ratio (CR): Jobs are processed according to smallest ratio of time remaining until due date to processing time remaining.Sequencing
Possible priority rules: First come. including the current one.

There will be no interruptions in processing such as machine breakdowns. Setup time is deterministic. or worker illness. Setup time is independent of processing sequence. no new jobs arrive after processing begins. Processing times are deterministic rather than variable.edu.
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http://www. and no jobs are canceled.Assumptions of priority rules: The set of jobs is known.tr/~kilter
.baskent. accidents.

Average number of jobs.tr/~kilter
. This is the length of time a job is at a particular workstation or work center.Performance Measures: Job flow time.edu. Makespan is the total time needed to complete a group of jobs. Makespan. This is the length of time the job completion date is expected to exceed the date the job was due or promised to a customer.baskent. It is the length of time between the start of the first job in the group and the completion of the last job in the group. Job lateness. Average number of jobs = Total flow time ÷ Makespan
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http://www. Jobs that are in a shop are considered to be work-inprocess inventory.

edu. Determine the sequence of jobs. and average number of jobs at the work center. the average flow time.Example
Processing times (including setup times) and due dates for six jobs waiting to be processed at a work center are given in the following table. average tardiness.tr/~kilter
.baskent. for each of these rules: FCFS SPT EDD CR
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Average tardiness: 54÷6 = 9 days.baskent.The FCFS sequence is simply A-B-C-D-E-F.tr/~kilter
. 2. Average flow time: 120÷6 = 20 days.93. 3. The measures of effectiveness are as follows (see table): 1. Average number of jobs at the work center: 120÷41 = 2.
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http://www.edu. The makespan is 41 days.

the job sequence is A-C-E-B-D-F (see the following table). The resulting values for the three measures of effectiveness are 1.63. 3.67 days.baskent.
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http://www. Average tardiness: 40÷6 = 6. Average flow time: 108÷6 = 18 days. 2.tr/~kilter
. Average number of jobs at the work center: 108÷41 = 2.Using the SPT rule.edu.

33 days.33 days. the job sequence is C-A-E-B-D-F. Average flow time: 110÷6 = 18. 2.68.edu.
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http://www.baskent. 3. Average number of jobs at the work center: 110÷41 = 2. Average tardiness: 38÷6 = 6.tr/~kilter
. The measures of effectiveness are as follows (see table): 1.Using earliest due date as the selection criterion.

edu.Using the critical ratio we find
At day 4 [C completed].tr/~kilter
.baskent. the critical ratios are
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http://www. the critical ratios are
At day 16 [C and F completed].

A. the critical ratios are
At day 23 [C. F.tr/~kilter
. and E completed]. the critical ratios are
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http://www. and A completed]. F.edu.baskent.At day 18 [C.

and the resulting values for the measures of effectiveness are as follows: 1. 3.edu.17 days. 2.67 days. Average flow time: 133÷6 = 22.baskent.
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http://www.24.tr/~kilter
. Average tardiness: 58÷6 = 9. Average number of jobs at the work center: 133÷41 = 3.The job sequence is C-F-A-E-B-D.

baskent.edu.22
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.

In addition. you will need to know the number of operations remaining.Example
Use the S/O rule to schedule the following jobs.tr/~kilter
.baskent.edu. including the current one. Note that processing time includes the time remaining for the current and subsequent operations.
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baskent. Divide the difference by the number of remaining operations.Determine the difference between the due date and the processing time for each operation. and rank them from low to high.tr/~kilter
. This yields the sequence of jobs:
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http://www.edu.

Job priorities cannot be used. All units in a job must be completed at the first work center before the job moves on to the second work center. All jobs must follow the same two-step work sequence.edu.
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http://www.baskent. several conditions must be satisfied: Job time (including setup and processing) must be known and constant for each job at each work center.Sequencing Jobs through Two Work Centers
For the technique to work. Job times must be independent of the job sequence.tr/~kilter
.

if the time is at the second work center.Determination of the optimum sequence involves these steps: List the jobs and their times at each work center. If the shortest time is at the first work center. working toward the center of the sequence. Select the job with the shortest time. schedule the job last. until all jobs have been scheduled.baskent. Eliminate the job and its time from further consideration.tr/~kilter
.
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http://www. schedule that job first.edu. Break ties arbitrarily. Repeat steps 2 and 3.

tr/~kilter
. The first operation involves cleaning and the second involves painting. Determine a sequence that will minimize the total completion time for this group of jobs.Example
A group of six jobs is to be processed through a two-machine flow shop.edu.baskent. Processing times are as follows:
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Select the job with the shortest processing time. We now have
The remaining jobs and their times are
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http://www.tr/~kilter
. schedule job D first.edu. Since it is at the second work center. schedule it last and eliminate job B from further consideration.baskent. with a time of two hours. Eliminate job D from further consideration. Since the time is at the first center. Job B has the next shortest time. It is job D.

Since it is for the first work center.The shortest remaining time is six hours for job E at work center 1. place it third in the sequence. Finally.baskent. schedule that job toward the beginning of the sequence (after job D). assign the remaining job (F) to the fourth position and the result is
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Job C has the shortest time of the remaining two jobs.edu. Thus. Thus.tr/~kilter
.

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http://www.tr/~kilter
.

baskent.Sequencing Jobs When Setup Times Are Sequence-Dependent
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http://www.edu.tr/~kilter
.

If that is not possible or feasible. Focusing on bottleneck operations: First. and then schedule the nonbottleneck operations around the bottleneck operations.edu.
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http://www. try to increase the capacity of the operations.Why Scheduling Can Be Difficult
Setting realistic due dates.baskent. Considering lot splitting for large jobs. This probably works best when there are relatively large differences in job times.tr/~kilter
. schedule the bottleneck operations first.

e.. Determine how to overcome (eliminate) the constraint.e..edu.tr/~kilter
.The Theory of Constraints
Determine what is constraining the operation. Subordinate everything to the constraint (i.baskent. make sure the constraining resource is used to its maximum). Repeat the process for the next highest constraint. Exploit the constraint (i.
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http://www. focus on the constraint).